1. Field of the Invention
This invention relates to machines for thinning crops. More particularly, the present invention relates to an improved apparatus for thinning row crops that allows selective adjustment of both the frequency and magnitude of plant removal in a thinning operation.
2. State of the Art
The early stages of plant development are full of risks. Temperature, humidity, rainfall, seed viability, sunlight, soil fertility, and other factors all affect whether a young plant will survive to maturity. Some crops, such as sugar beets, are particularly vulnerable in their early stages. To deal with these crop risks, growers typically plant more than the desired stand of crop as insurance against early plant loss. Then, when the plants have grown enough to be likely not to succumb to the above-mentioned dangers, the growers will reduce the number of plants by thinning if the surviving plant population is too high. Thinning involves removing some portion of the young plants, preferably the smallest and least healthy, before they have a chance to grow to maturity.
Traditionally, thinning has been performed by manual labor. However, with changes in agricultural methods and labor practices, manual labor has become very expensive. Consequently, thinning machines have been developed to perform the same task. These machines fall into two categories: selective thinning machines; and random thinning machines. Selective thinning machines use on-the-fly data collection to select which plant to keep and which to eliminate. As will be appreciated, selective thinning machines tend to be quite complex, expensive, and slow. Random thinning machines simply eliminate plants based on an average population desired. Random thinners are less expensive than selective thinners, but they still tend to be slow, and they are generally nonadjustable--one machine will always thin at a certain rate, and leave a crop at a certain spacing and a certain population, regardless of the crop or other conditions. In addition, some random thinning machines operate by dragging a thinning mechanism transversely across the rows of crops. It will be apparent that such an operation is undesirable because it tends to damage crop and irrigation rows, and is especially difficult in those regions which rely upon flood irrigation. Moreover, conventional random thinning machines typically employ only one shape or size of cutting blade, which makes the machine somewhat inflexible.
It would thus be desirable to have a random crop thinner that is designed to operate parallel to crop rows, and is adjustable for a variety of crops and conditions, yet is still simple and inexpensive. It would also be desirable to have a simple, random crop thinner which employs removable blades, such that a single machine may accommodate a variety of plant types and row conditions.